1. Field of the Invention
The present invention relates to a nonvolatile semiconductor memory device and, more particularly, to a nonvolatile semiconductor memory device having a multilayered oxide and nitride film.
2. Description of the Related Art
Micropatterning of Nonvolatile Semiconductor memory elements poses the problem of an increase in interference between adjacent cells. This makes it necessary to decrease the thickness of a multilayered oxide and nitride film used as an interelectrode dielectric film. In addition, to reduce a leakage current that flows through the interelectrode dielectric film when its thickness decreases, a multilayered oxide and nitride film having nitride films in the upper and lower interfaces is already proposed.
In an dielectric film having oxide films in the upper and lower interfaces, it is possible by post oxidation after cell processing to reduce a leakage current caused by the damage during the processing, and a leakage current caused by a pointed end face of an electrode layer (e.g., Jpn. Pat. Appln. KOKAI Publication No. 2003-31705).
Unfortunately, in an interelectrode dielectric film having nitride films in the upper and lower interfaces (e.g., U.S. Pat. No. 5,661,056), the influences of the leakage current caused by the damage during the processing and the leakage current caused by the acute-angled electrode end face remain.